1. Field of the Invention
This invention relates broadly to polymer matrix compositions. More particularly, this invention relates to a thermoset polymer matrix having multiple layers, each formed from any of a variety of thermoset polymer resins and having any of a variety of functional agents suspended within the resin.
2. State of the Art
Polymer resin technology and methods of forming structures using thermoset resins are well known in the prior art. Thermoset polymer materials and equipment are commonly used in the medical industry as well as in other industries. Embedding or coating such structures with anti-microbial agents is also known in the industry. For example, U.S. Pat. No. 5,817,325 of Sawan et al. discloses contact killing anti-microbial articles, devices and formulations whose contact killing properties can be applied to the surface of an object or are contained within an article which is intended to contact biological tissues. The antimicrobial layer is either applied secondarily to the article or device or cast into the article or device as the article or device is formed. Sawan teaches that the anti-microbial material is an organic polycationic polymer matrix such as a biguanide polymer having bound or complexed thereto a surface-accessible anti-microbial metallic material (biocide). The polymer matrix must be capable of reversibly binding or complexing with the biocide and also be capable of subtly infusing the biocide into the cell membrane of the microorganism. According to Sawan, it is preferable that the organic material be capable of dissolving into or adhering to the microorganism""s cell membrane.
U.S. Pat. No. 5,478,563 to Erami discloses an antibacterial and anti-fungal composition formed from a polyacetal base resin and antibacterial and/or anti-fungal agents melt-blended or directly added to the polyacetal base resin such that resin and agents completely combine to form a homogeneous resin mixture; i.e., a mixture in which the agents are soluble and dissolve into the resin.
U.S. Pat. No. 5,827,524 to Hagiwara et al. discloses a porous crystalline anti-microbial polymer composition which is coated on a silica gel substrate, heated, and then sintered to form, or which may then be mixed with a polymer to provide the polymer structure with antimicrobial properties. The polymer structure is thereby uniformly provided throughout its thickness, with the antimicrobial polymer composition. As such, the antimicrobial composition, which is relatively expensive, is even provided in central portions of the structure, where it cannot act against microbial agents.
It is therefore an object of the present invention to provide a composite thermoset structure having a plurality of thermoset polymer matrix layers.
It is another object of the invention to provide a composite thermoset polymer matrix having one or more agents heterogeneously suspended therein, where the polymer matrix can then be utilized in a structure.
It is an additional object of the present invention to provide composite thermoset polymer matrix structures having a plurality of polymer matrix layers homogeneously bonded together, where each layer is formed from a composition of any of a variety of thermoset polymer resins and any of a variety of agents or combination of agents heterogeneously dispersed within the thermoset polymer resin such that each layer exhibits a distinct desirable functional property or characteristic.
It is a further object of the present invention to provide a composite thermoset polymer structure having a plurality of homogeneously bonded thermoset polymer matrix layers with each layer exhibiting any of a variety of distinct desirable properties including but not limited to anti-microbial properties, anti-fungal properties, anti-viral properties, anti-thrombotic properties, friction reducing properties, radiopacity properties, and thermo-electrical resistance or conductive properties.
Another object of the invention is to provide a great variety of composite thermoset polymer matrix structures including tubes, sheets, wire coatings, and tapes which have any of a variety of desirable properties included within a polymer matrix structure.
In accord with these objects, which will be discussed in detail below, a composite thermoset polymer matrix structure has a plurality of homogeneously bonded thermoset polymer layers; i.e., each layer is bonded to the other such that the plurality of layers mechanically functions as a single layer. Such homogeneous bonding is a combination of adhesion, cross-linking, and hydrogen bonding. Each of the layers is formed from either a pure thermoset polymer resin or a composition of any of a variety of thermoset polymer resins and any of a variety of agents or combination of agents heterogeneously dispersed and suspended within the thermoset polymer resin. In this manner, each layer exhibits a distinct desirable functional property or characteristic depending upon an intended application. Various structures such as a polymer tape, wire coating, sheet and tube are provided. In forming the structures, each layer of the structure is preferably formed from a plurality (typically numerous) sublayers, all of the same composition.
It will be appreciated that the composite thermoset polymer matrix structure may be formed into any size or any shape, object, or structure. It will further be appreciated that the arrangement and composition of the homogeneously bonded composite thermoset polymer matrix layers may be varied depending upon the desirable qualities, properties, or characteristics required by the intended application.
The thermoset polymer resin used to form the composite thermoset polymer matrix layers of the present invention may be selected from any of a plurality of thermoset polymer resins which have homogeneous bonding characteristics including but not limited to polyimide, polyurethane, polyester, polyamide-imide, and polyamide. According to the preferred embodiment the thermoset polymer resin used to form the matrix is polyimide.
According to one aspect of the invention, the agents dispersed and suspended in each layer of the polymer matrix are selected from a group of additives including but not limited to anti-microbial agents, anti-fungal agents, anti-viral agents, anti-thrombotic agents, friction reducing agents, radiopaque agents, and electrically conductive or resistive agents. Any of a variety of anti-microbial agents may be added to the thermoset polymer resin, but silver ion producing agents carried in a zeolite carrier are preferred. Likewise, any of a variety of anti-fungal agents, anti-viral agents, anti-thrombotic agents, etc. can be utilized. While the radiopaque agents, and the electrically conductive agents, may be added to any layer within the matrix structure, it is preferable that the anti-microbial agents, the anti-fungal agents, the anti-viral agents, the anti-thrombotic agents, and the friction reducing agents be added to an exposed surface layer of the matrix.
According to another aspect of the invention, the agents suspended in the matrix remain in powder form, have a particulate size (diameter) of up to 5 microns, and constitute up to thirty percent by weight of the finished solid plastic material.
A method of forming the composite thermoset polymer matrix is also provided. The method of forming a solid plastic structure from a thermosetting polymer resin or resin suspension generally includes applying a liquid polymer resin to an object or forming a layer coated on a mandrel, and heating the polymer resin until it cures to form a first layer. If multiple sublayers of the same resin are desired, the process is repeated. Once a first thermoset polymer resin layer is cured, additional thermoset polymer resin layers may be applied to it using the same technique detailed above.
According to the invention, at least one of the layers is provided with an agent additive heterogeneously suspended within the resin. This is accomplished by mixing any of a variety of liquid thermoset polymer resins with any of a variety of agents or combination of agents in a powdered particulate form until the powdered particulate is evenly dispersed throughout the liquid resin. Once evenly dispersed, a true heterogenous thermoset polymer mixture is formed. A true heterogenous mixture means that the powdered particulate added is merely suspended and encased within the liquid resin; i.e. no chemical bonding or polymerization between the powdered particulate and the resin occurs.
A composite thermoset polymer matrix sheet is formed by pouring a first layer of the liquid thermoset polymer resin (with or without additives) into the form of a flat sheet, heat curing the first layer, and then applying additional composite thermoset polymer resin suspension layers with one or more additives to the first layer as described above.
A composite thermoset polymer matrix wire coating is formed by coating a metal substrate, preferably a copper wire, with the liquid thermoset polymer resin and then heat curing the thermoset polymer resin as described above. Any number of layers with different additives may be applied to the metal substrate, one atop another, until a desired matrix thickness is achieved. A composite thermoset polymer matrix tube is produced by removing the metal substrate from within the composite thermoset polymer matrix layers after the desired matrix thickness is achieved.
The thermoset polymer matrix structures described above have numerous possible applications within a variety of technologies and industries including the medical technology industry, research and development technologies, the oil and gas industry, aviation and space exploration, and electrical design industries.
Additional objects and advantages of the invention will become apparent to those skilled in the art upon reference to the detailed description taken in conjunction with the provided figures.